This invention relates to a packaging machine and to a method of filling flexible pouches with product, evacuating air from the filled pouches, and then sealing the pouches.
In the packaging of certain products, and particularly food products, the filled and sealed pouches are delivered to an autoclave or retort and are heated to high temperatures so as to sterilize the product in the pouches. In order for this packaging process to be successful, it is important that the sealed pouch be substantially free of air when the pouch is delivered to the autoclave. If any significant amount of air is present in the pouch, the air will expand when subjected to the high temperatures in the autoclave and will cause the pouch to balloon, such ballooning sometimes destroying the seals of the pouch. Even if the pouch is not subjected to autoclaving, it is often desirable to remove the air from the pouch so that the product will be packaged in an oxygen-free environment and will possess a long stable shelf life.
One known method of removing air from pouches is disclosed in Johnson U.S. Pat. No. 4,081,942 in which filled pouches are advanced beneath a steam nozzle and then are sealed while steam is being directed out of the nozzle and into the pouches. The steam purges the pouches of air and then condenses to create a vacuum in the pouches.